The field of this invention is immunogenic compositions comprising bacterial proteases and/or peptides derived therefrom, more particularly those of Porphyromonas gingivalis, most particularly the arginine-specific proteases and immunogenic compositions containing Arg-gingipains and/or peptides derived therefrom, and the lysine-specific proteases termed Lys-gingipains herein and immunogenic compositions containing Lys-gingipain(s) and/or peptides derived therefrom. Those immunogenic compositions are useful in the protection of a mammal, including a human, from infection and pathology caused by P. gingivalis.
Porphyromonas gingivalis (formerly Bacteroides gingivalis) is an obligately anaerobic bacterium which is implicated in periodontal disease. P. gingivalis produces several distinct proteolytic enzymes; its proteinases are recognized as important virulence factors, together with other factors such as lipopolysaccharide and a polysaccharide capsule, fimbriae, lectin-like adhesins, hyaluronidase, keratinase, superoxide dismutase and hemagglutinating and hemolyzing activities. A number of physiologically significant proteins, including collagen, fibronectin, immunoglobulins, complement factors C3, C4, C5, and B, lysozyme, iron-binding proteins, plasma proteinase inhibitors, fibrin and fibrinogen, and factors of the plasma coagulation cascade system, are hydrolyzed by P. gingivalis proteases. Broad proteolytic activity plays a role in the evasion of host defense mechanisms and the destruction of gingival connective tissue in progressive periodontitis [Saglie et al. (1988) J. Periodontal. 59:259-265].
Progressive periodontitis is characterized by acute tissue degradation promoted by collagen digestion and a vigorous inflammatory response characterized by excessive neutrophil infiltration [White and Maynard (1981) J. Periodontal Res. 16:259-265]. Gingival crevicular fluid accumulates in periodontitis as periodontal tissue erosion progresses at the foci of the infection, and numerous plasma proteins are exposed to proteinases expressed by the bacteria at the injury site. Neutrophils are recruited to the gingiva, in part, by the humoral chemotactic factor C5a. The complement components C3 and C5 are activated by complex plasma proteases with "trypsin-like" specificities called convertases [Muller-Eberhard (1988) Ann. Rev. Biochem. 57:321-347]. The human plasma convertases cleave the .alpha.-chains of C3 and C5 at a specific site generating biologically active factors known as anaphylatoxins (i.e. C3a and C5a). The anaphylatoxins are potent proinflammatory factors exhibiting chemotactic and/or spasmogenic activities as well as promoting increased vascular permeability. The larger products from C3 and C5 cleavage (i.e. C3b and C5b) participate in functions including complement cascade activation, opsonization, and lytic complex formation.
There are conflicting data as to the number and types of proteinases produced by P. gingivalis. In the past, proteolytic activities of P. gingivalis were classified into two groups; those enzymes which specifically degraded collagen and the general "trypsin-like" proteinases which appeared to be responsible for other proteolytic activity. Chen et al. (1992) J. Biol. Chem. 267, 18896-18901 reported the first rigorous purification and biochemical characterization of an arginine-specific P. gingivalis protease; the purification of a lysine-specific proteinase of P. gingivalis is described by Pike et al. (1994) J. Biol. Chem. 269:406-411 [see also Potempa et al. (1995) Perspectives in Drug Discovery and Design 2:445-458].